Stabilized nickel powder



Patented Nov. 8, 1949 STABILIZED NICKEL POWDER Owen G. Bennett,Baltimore, Md., assignor to Catalyst Research Corporation, Pittsburgh,Pa., :acorporation of Maryland N Drawing.

Application March 13, 1948,

Serial No. 14,823

Claims.

This invention relates to finely divided nickel. Finely divided nickelmay be produced by a method disclosed in U. S. Patent No. 1,893,879,granted January 10, 1933, on an application filed by the presentapplicant and J. C. W. Frazer. In accordance with the invention of thatpatent a nickel amalgam is subjected to vacuum distillation, in theabsence of gas reactive with nickel, to completely evaporate the mercuryand leave the nickel as a residue. Nickel thus produced possessesunusual properties. For example, the particle size is so small that theresultant nickel powder will smear on glass much in the manner thattalc'does. An outstanding property of such nickel is that it isexceptionally reactive relative to finely divided nickel produced inother ways.

Nickel produced in this way from a nickel amalgam is particularly usefulfor the production of exothermic compositions, and particularly fusepowders. For instance, high speed fuse compositions composed of thisform of nickel and sulfur, with or without an inert diluent to regulatethe burning speed, are disclosed in Patent No. 2,434,067, grantedJanuary 6, 1948, on an application filed by J. C. W. Frazer andthepresent applicant.

This form of nickel is especially useful in the production of delay fusecompositions. Particularly desirable compositions of this type aredisclosed in a co-pending application, Serial No. 469.978. filedDecember 24, 1942, now Patent No. 2,440,579, granted April 2'7, 1948, byJ. C. W. Frazer and the present applicant, and assigned to the assigneeof the present application.v In accordance withthat invention delaycompositions are composed of nickel of the aforesaid crigin and anoxidizing agent such as a per-salt of an. oxygen-containing acid, mostsuitably potassium perchlorate, with or without an inert diluent, suchas diatomaceous earth. Nickel in this form is useful also with othertypes of delay fuse compositions, for example those'disclosed incopending application Serial No. 600,415, filed June 19, 1945, by thepresent applicant and J. Dubin, now U. S. Patent No. 2.457.860 andlikewise owned by the assignee of the present application. Thecompositions of that co-pending application comprise this form of nickeltogether with finely divided zirconium, an oxidizing agent adapted tooxidize those metals at a high rate of speed, for example an alkalimetal perchlorate, and an oxidizing agent adapted to oxidize them at aslow rate of speed; for example barium chromate.

A particular feature of such composition is that their burning times maybe varied not only by variation of the oxidizing agent used but also byvariation in the proportions of oxidizing agent to metal and of inertdiluent, when used. Those compositions also are characterized by thefact that they burn without production of gaseous products of combustionto form solid residues so that the fuses need not be vented to theatmosphere, which is recognized as highly desirable for ordnancepurposes.

Nickel produced in accordance with Patent No. 1,893,879 is so reactive,that it is pyrophoric in nature, i. e., it ignites upon exposure to airand other oxidizing gases. However, if before contact with oxygen thenickel powder is contacted with carbon dioxide it may be handled freelythereafter in air without danger of ignition so that it can then be usedfor various purposes, as for the compounding of the foregoing fusecompositions.

Extended experience has shown that if fuse compositions of the kindsalluded to are made from such carbon dioxide-treated nickel promptly orwithin a short time after its production, the burning time of thecompositions changes progressively upon storage, which is obviouslyundesirable because of the requirement that a delay fuse burn within arigidly defined period of time. On the other hand, experience has shownlikewise that if after being treated with carbon dioxide the finelydivided nickel be stored for a sub-' is objectionable in that itrequires the carrying of greater stocks of nickel than would otherwisebe necessary, with attendant cost, coupled with the inability to supplyfuse compositions promptly after'production of the nickel powder. It isundesirable also because it is by no means certain that the aging ofevery batch of amalgam-produced and carbon dioxide-treated nickel for agiven length of time will result in complete aging.

The primary object of the present invention is to provide a method oftreating nickel produced by evaporation from nickel amalgam to renderit, and compositions containing it, insensitive to alteration uponstorage, which is simple, inexpensive, easily practiced, and productiveof nickel powder that is stabilized against oxidation and is useful formaking fuse and other compositions 3 that reliably maintain over longintervals of time predetermined burning rates.

Other objects will appear from the following specification.

I have discovered, and it is upon this that the present invention ispredicated, that the necessity for aging nickel produced by the vacuumdistillation of mercury from a nickel amalgam as described in Patent No.1,893,879, and treated with carbon dioxide prior to contact with oxygento render it non-pyrophoric, can be eliminated by the simple expedientof heating the carbon dioxide-treated nickel in air, or a similaroxidizing gas, for a short period of time.

In the practice of the invention the nickel after treatment with carbondioxide, and as promptly thereafter as may be desired, is placed in acontainer to which air has free access, and the powder is then heated.The exact temperature of heating is not material to the efficacy of thetreatment provided the powder does not reach a temperature at which itwill ignite while bein so heated. The heating is continued for a time,dependent upon the applied temperature, to render the nickel stableagainst further oxidation upon storage. The higher the temperature, withthe limitation just noted, the more rapid will be the stabilization ofthe nickel against further change. Thus, the stabilizing effect will beproduced more rapidly at 200 than at 100 C. I find that thestabilization is effected rapidly and without damage of ignition of thenickel by heating for about 30 minutes at 300 0., which constitutes thepreferred practice of the invention.

Heating for a longer time than necessary to stabilize the nickel againstfurther change is merely uneconomical.

Extended experience has shown that fuse compositions made from nickeltreated in the manner just described, for example compositions inaccordance with the inventions of the aforesaid copending applicationsand Patent No. 2,434,067 do not undergo alteration of burning time, atleast within permissible ordnance limits, upon pro longed storage, andthus the necessity for aging such amalgam produced nickel prior to thisinvention is eliminated and predetermined and sustained burning timesare more reliably attained. Moreover, the compositions remain unafiectedby extremes of temperature and humidity experienced in transportationand storage in temperate and tropical climates.

While I do not commit myself to this, or any other theory, I now believethat the alteration in burning time alluded toabove as occurring withfuse compositions made from this finely divided nickel promptly afterits. production. is due to a slow, progressive oxidation of the nickel,and further that the heating with free access of oxygen in accordancewith the present invention promptly causes the nickel to be oxidized, tothe same extent so that it does not undergo any further oxidation, or atleast to any detrimental extent, upon long continued storage. Queerlyenough, the exceptional reactivity that makes this form of nickel sodesirable for fuse compositions is not depreciated materially.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have described what I now consider torepresent its best embodiment. However, I

- desire to have it understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

I. claim:

1. That method of stabilizing nickel produced by evaporation of mercuryfrom a nickel amalgam which comprises contacting the said nickel withcarbon dioxide prior to contact with oxygen, and then heating it in agas containing free oxygen at a temperature below that at which thenickel ignites while being so heated.

2. That method of stabilizing nickel produced by evaporation of mercuryfrom a nickel amalgam which comprises contacting the said nickel withcarbon dioxide prior to contact with oxygen, and then heating it in airat a temperature below that at which the nickel ignites while being soheated for a time to stabilize it against further substantial oxidationupon long continued storage.

3. A method according to claim 1, said nickel being heated between about200 and about 300 C;

4. A method according toclaim 2, said nickel being heated at about 300C.

5. That method comprising the steps of sub.- jecting a nickel amalgam tovacuum distillation in the absence of gas reactive with nickel to evap'orate mercury therefrom and leave a. residue of nickel in finely dividedform that is highly reactive with oxygen, then, prior to contact withoxygen, contacting the said nickel residue with carbon dioxide, and thenheating the nickel in air at a temperature below that at which thenickel ignites when so heated, and thereby stabilizing the nickelagainst further substantial oxidation by atmosphere oxygen upon storage.

OWEN G. BENNETT.

REFERENCES CITED The following references are of record in thefile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,001,279 Kayser Aug. 22, 19111,127,911 Morey Feb. 9, 19 15 1,987,660 Bennett et al. Jan. 15, 1935v2,205,552 Arnold June 25, 1940 FOREIGN PATENTS Number Country Date 4,702Great Britain, 1912 May 26, 1913

